Research ArticleDesign of Yagi Antenna with Slow-Wave Half-Mode SIW FeedingTechnique for Ku Band Applications
Bo Han,1,2 Shibing Wang,1 Jia Zhao,1 and Xiaofeng Shi1
1School of Computer and Information Engineering, Fuyang Normal University, Fuyang 236037, China2State Key Laboratory of Millimeter Waves, Southeast University, Nanjing 210096, China
A novel planar Yagi antenna printed on a microwave substrate with dielectric constant of 3.55 for Ku band applications has beenpresented in this paper. The proposed antenna has been fed by the slow-wave half-mode substrate-integrated waveguide and hasachieved good characteristics, such as reduced size, high gain, broadband, and low insertion loss. The proposed antenna hasbeen fabricated by Rogers 4350 substrate with lengths of two arms for dipole 0.46 λ0. Measured results indicate that theimpedance bandwidth (below −10 dB return loss) is from 15.4GHz to 19.4 GHz with peak gain 7.49 dBi. Both simulations andexperiments convince that the proposed antenna could have reliable applications for Ku band wireless communications.
1. Background and Introduction
The planar Yagi antenna becomes a popular opportunity forthe design of wireless communication system as advantagesof low complexity, low cost, low profile, lightweight, and easyintegration. Many researchers have done numerous studyworks on the design of Yagi antenna. Practically, the feedingsystem plays an important role in the performance of theYagi antenna. The quasi-Yagi antenna and array fed by themicrostrip-to-CPS balun have been proposed in [1, 2],respectively. Extremely wide frequency bandwidth and goodradiation characteristics have been achieved by this feedingtechnique. The substrate-integrated waveguide (SIW) tech-nologies have been proposed to combine the advantagesof rectangular waveguide and microstrip circuits [3, 4].Substrate-integrated folded waveguides (SIFW) and half-mode substrate-integrated waveguide (HMSIW) have beenproposed to reduce the size of SIW in [5, 6], respectively.The design of a miniaturized substrate-integrated waveguideusing embedded split-ring resonators has been illustrated in[7, 8]. Yagi antennas fed by SIW and HMSIW have been pre-sented in [9, 10], in which high gain and broadband haveachieved with a simple structure. Recently, the slow-wavesubstrate-integrated waveguide (SW-SIW) by a double-
layer substrate with the bottom layer including metallizedvia-holes connected to the ground has been proposed in[11]. Compared with the classical SIW, the SW-SIW canreduce the longitudinal dimension by more than 40% as thephase velocity is significantly smaller than the SIW structure.
In the paper, a novel planar Yagi antenna fed by the slow-wave half-mode SIW (SW-HMSIW) has been proposed forKu band applications. The proposed antenna has beenfabricated by a conventional PCB process with compact size21.1× 13.4× 1.016mm3. Measured results show that theimpedance bandwidth is from 15.4GHz to 19.4GHz withan average gain of more than 8.1 dBi.
This paper is organized as follows. Section 2 describes thedesign of the proposed SW-HMSIW and SW-HMSIW-fedplanar Yagi antenna. Section 3 presents the electromagneticsimulations and experimental results of the proposed Yagiantennas. Finally, the summary and conclusion are givenin Section 4.
2. Design of Proposed SW-HMSIW-Fed YagiAntenna
In this section, the design of slow-wave SIW and SW-HMSIW-fed Yagi antenna is illustrated in detail.
HindawiInternational Journal of Antennas and PropagationVolume 2017, Article ID 5827181, 7 pageshttps://doi.org/10.1155/2017/5827181
2.1. Design of Slow-Wave SIW. The layouts of the substrate-integrated waveguide and half-mode substrate-integratedwaveguide have been shown in Figure 1, whereW4 representsthe distance between the two rows of vias and H representsthe height of the Rogers 4350 dielectric substrate. For theRogers 4350 substrate, the relative permittivity εr is 3.45,the value of tangent for the loss angle is 0.004, and thethickness of the metal is 50 microns. The diameter of themetallized via in the dielectric substrate R is 0.4 millimeters,and the center distance between the metallized vias D is0.8 millimeters.
The layout of the slow-wave half-mode substrate-integrated waveguide with the same geometry size has beenshown in Figure 2. There are two layers of dielectric substratewhich are made up of Rogers 4350 substrate with diameter ofthe metallized via 0.4 millimeters for the SW-HMSIW struc-ture. In order to realize slow-wave effect, three rows of met-allized vias as shown in Figure 2(b) are designed in medium2. The bottoms of these rows’ metallized vias are connected
to the ground while the tops are suspended. The value ofthe central distance between adjacent two rows of metallizedvias D1 is 0.9 millimeters. All values of physical dimensionsfor these substrate-integrated waveguides designed on Rogers4350 substrate have been shown in Table 1.
Figure 2: Slow-wave substrate-integrated waveguide layout fabricated by Rogers 4350 substrate. (a) Top view; (b) cross-section view.
Table 1: Values of substrate-integrated waveguide geometryparameters designed on Rogers 4350 substrate (all units inmillimeters).
Parameters Values Parameters Values
W1 6.8 L1 28
W2 2.2 L2 6
W3 4 L3 4
W4 6 W5 1.76
R 0.4 D 0.8
H1 0.508 D1 0.9
H2 0.508
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The proposed substrate-integrated waveguides have beencomputed by Ansoft’s HFSS software, and the simulationport is set as a lumped port [12]. The simulated surfaceE-filed distributions for the SIW, HMSIW, and SW-HMSIW at 20GHz have been shown in Figure 3. It can beseen that three propagation cycles of E filed are illustratedfor the SIW and HMSIW. However, the number of theE-filed propagation cycle is four for SW-HMSIW. Therefore,the slow-wave effect can be well explained graphically.
Figure 4 shows the simulated scattering parameters forthe different mode substrate-integrated waveguides. Accord-ing to this diagram, the cutoff frequency of HMSIW is
10.35GHz. Compared to the structure HMSIW, the cutofffrequency of the SW-HMSIW is reduced by 1.2GHz. Hence,a narrower waveguide could be obtained when an SW-HMSIW is used instead of a conventional HMSIW for thesame targeted cutoff frequency [9].
2.2. Design of SW-HMSIW-Fed Yagi Antenna. The layout ofthe proposed slow-wave half-mode substrate-integratedwaveguide Yagi antenna which consists of two layers ofRodgers 4350 substrate has been plotted in Figure 5. In thetop view, there are a truncated metal plane acted as the toplayer of the SW-HMSIW, one of the parallel lines, one armof the dipole antenna, and four director elements. A row ofmetallized vias which connect the top metal and groundmetal through two dielectric substrates acts as the side-wall of the SW-HMSIW. The bottom substrate consists
(a)
(b)
(c)
Figure 3: Simulated surface E-filed distribution of substrate-integrated waveguides at 20GHz. (a) Substrate-integratedwaveguide; (b) half-mode substrate-integrated waveguide; (c)slow-wave half-mode substrate-integrated waveguide.
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4 10 16 22 28Freq (GHz)
S11
(dB)
SIWHMSIWSW-HMSIW
Figure 4: Simulated |S11| parameters of different mode substrate-integrated waveguides.
L2 D7D6
W5
W5
D5
D2
Wsiw
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D
D4
D3
W3
W4
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Figure 5: Layout of the proposed slow-wave half-mode substrate-integrated waveguide Yagi antenna designed on Rogers 4350substrate. (a) Top view; (b) bottom view.
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a truncated ground plane as the other layer of the SW-HMSIW, the second arm of the dipole antenna, and fourdirector elements printed in the opposite direction. Inorder to reduce the design parameters, all of the width,length, and space between the director elements are setup equal to each other. There are four rows of metallizedvias designed in the sublayer dielectric substrate with topsuspended. The occupying area of the proposed antennais only 21.1× 13.4mm2. To feed the antenna with a sub-miniature version A (SMA) connector, a microstrip linewith width (W5) of 1.4 millimeters is designed. All valuesof the geometry parameters for the proposed Yagi antennahave been illustrated in Table 2.
The proposed SW-HMSIW-fed Yagi antenna has beensimulated, physically fabricated, and practically measured.The computation of the proposed antenna is done byAnsoft’s HFSS software, and the measurement of S-parame-ters is made out by the Agilent vector network analyzerN5227A. The photos of the fabricated antenna with Rogers4350 substrate have been shown in Figure 6. Figure 7shows the comparison of |S11| for the computed HMSIW,computed SW-HMSIW, and measured SW-HMSIW-fedYagi antennas. According to the −10 dB level line, thesimulated bandwidth of the HMSIW-fed antennas is from
Table 2: Values of the geometry parameters for the proposed Yagiantenna (all units in millimeters).
Parameters Values Parameters Values
W1 13.4 L1 21.1
Wsim 2.2 D2 1
W3 2.5 L2 9.54
W4 4.4 W5 1.4
R 0.4 D 0.8
H1 0.508 D1 0.8
H2 0.508 D3 1
D4 1.9 D5 0.5
D6 4.5 D7 2
W6 2.5
(a)
(b)
Figure 6: Photos of the fabricated slow-wave SIW Yagi antennafabricated by Rogers 4350 substrate. (a) Top view; (b) bottom view.
Figure 7: The comparison of |S11| for the computed HMSIW,computed SW-HMSIW, and measured SW-HMSIW-fed Yagiantennas.
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0
11 15 19 23Freq (GHz)
S11
(dB)
𝜀r = 3.45 Rogers 4350𝜀r = 3.9𝜀r = 4.4Measured
Figure 8: Computed S11 values for the proposed metamaterialantennas with different relative permittivity.
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16.24GHz to 19.3GHz with absolute bandwidth 3.06GHz,the simulated SW-HMSIW antennas is from 16.2GHzto 20.3GHz with absolute bandwidth 4.1GHz, and themeasured bandwidth is from 15.4GHz to 19.4GHz withabsolute bandwidth 4.0GHz. As can be seen, comparedto the conventional HMSIW-fed Yagi antenna, the pro-posed antenna has better impedance matching perfor-mance. A reasonable agreement between the simulationsand measurements has been found convincing that theproposed antennas have reliable applications for Ku bandwireless communications. To further analyze the deviationof S11 between the experiment and simulation, the com-puted S11 values of the antennas with different relativepermittivity have been shown in Figure 8. It is obviousthat the deviation of S11 is mainly caused by the deviationdielectric constant.
The simulated surface current distribution of proposedSW-HMSIW-fed antenna at different frequencies (12GHzand 18GHz) has been shown in Figure 9. As can be illus-trated, the maximum surface current is concentrated in thebottom side of the Yagi antenna at nonworking frequencyband (12GHz). While at the operating frequency (18GHz),the distribution of surface current is more uniform. The3-D radiation patterns of the proposed antennas at 12GHzand 18GHz have been shown in Figure 10. It can be observedthat the main beam of the proposed antennas becomes in theend-fire direction in the operating bandwidth.
The measured and simulated 2-D radiation patterns ofthe proposed Yagi antenna at different frequencies have beenshown in Figure 11. The variations of simulated and mea-sured peak-realized gain (dBi) and radiation efficiency withfrequency for the proposed antenna have been shown in
(a) (b)
Figure 9: Simulated surface current distribution of proposed Yagi antenna at different frequencies: (a) 12GHz; (b) 18GHz.
(a) (b)
Figure 10: 3-D radiation patterns of the proposed Yagi antenna designed on Rogers 4350 substrate at different frequencies: (a) 12GHz;(b) 18GHz.
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Figure 12. The average simulated and measured gains of theproposed antennas are 8.1 dBi (with the peak of 8.5 dBi at19.2GHz) and 5.25 (with the peak of 7.49 dBi at 19GHz),respectively. The comparison of antenna performance fordifferent feeding techniques has been shown in Table 3.It is obvious that the characteristics of the high gain,broadband, low insertion loss, and simple design for theproposed Yagi antenna have been verified by the simulatedand measured results.
4. Summary and Conclusions
In this paper, the slow-wave HMSIW with Rogers 4350substrate has been computed and studied. Compared with
the classical SIW, the SW-HMSIW can reduce the longitu-dinal dimension as the phase velocity is significantlysmaller than the SIW structure. A novel SW-HMSIW-fedYagi antenna has been simulated, physically fabricated,and practically measured. Good characteristics of the Yagiantenna, such as reduced size, high gain, broadband, and
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Figure 11: Measured and simulated 2-D radiation patterns of the proposed Yagi antenna at different frequencies (solid line: simulated data;line with circle symbol: measured data): (a) 15GHz; (b) 18GHz.
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4.5
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gai
n (d
bi)
SimulatedMeasured
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90%
100%
11 15 19 23Freq (GHz)
Radi
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cy
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Figure 12: Variation of peak-realized gain (dBi) and radiation efficiency with frequency: (a) peak-realized gain; (b) radiation efficiency.
Table 3: The comparison of antenna performance for differentfeeding techniques.
Feeding technique Size Bandwidth Gain
Microstrip-to-CPS balun Poor Medium Medium
HMSIW Medium Medium Medium
SW-HMSIW Good Good Medium
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low insertion loss, have been verified by the computationand experiment. Measured results indicate that the imped-ance bandwidth of the proposed antenna is from 15.4GHzto 19.4GHz with the peak gain 7.49 dBi. The 3-D radiationpatterns of the proposed antenna show that the mainbeam of the proposed antennas is in the end-fire directionin the operating bandwidth. All of these convince that theproposed antennas have reliable applications for Ku bandwireless communications.
Conflicts of Interest
The authors declare that they have no conflicts of interest.
Acknowledgments
This study is supported in part by the National NaturalScience Foundation of China (nos. 61401101 and 61672006),the Anhui Provincial Natural Science Foundation (nos.1708085MF155 and 1608085QF159), the Natural ScienceKey Foundation of Anhui Provincial Universities (no.KJ2017A333), and the Anhui Provincial OutstandingTop-notch Talent Cultivation Project (gxfxZD2016164).
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